Dinosaurs are a diverse group of terrestrial vertebrate animals belonging to the dinosauria clade. It is from the greek meaning "terrible lizard" and was coined in 1842 by Richard Owen.

Dinosaurs arose in the early Triassic, around 231 million years ago, from archosaurs (a division including dinosaurs, crocodiles, pterosaurs, and many other less well known groups), and radiated in the early-mid Jurassic, reaching their greatest diversity around the late Jurassic and early Cretaceous. Most lineages of dinosaurs became extinct during the Cretaceous–Paleogene (K-Pg Event) extinction event(s)[1] 66 million years ago. The dinosaur phylogeny survives today only in birds.

Dinosaurs in popular culture have often been depicted as giant, lumbering, and cold-blooded beasts. In reality, the group was highly diverse with organisms ranging in size from 28 cm ('Ashdown Maniraptor' — unknown species[2]) to 60 m in length (Amphicoelias — rough estimate) and were dynamic, active animals. As a whole, dinosaurs were highly likely to have been warm-blooded. This is reflected in the development of feathers in the theropods (the bipedal, largely carnivorous dinosaurs) as insulators.

There are two major clades of dinosaur, which are based on an early divergence in the structure of the hip joint in the mid Triassic:

Saurischians (from Greek meaning "Lizard hip") including two major groups:

Theropods - Bipedal animals that were mostly carnivorous and contain some of the most well known dinosaurs (Tyrannosaurs and Velociraptor). They are generally considered to be the most intelligent group of dinosaurs and this is reflected by their relatively large brain cases. There is also evidence of complex social behavior similar to that of modern birds. This group includes the smallest dinosaur ever discovered and this lineage gave rise to aves (extant birds).

Sauropods - Quadrupedal animals that were almost certainly all herbivorous (however, some early Prosauropods were likely omnivorous). The group developed elongated necks and tails as well as columnar limbs to support their massive bulk. They had a large gut for processing tough plant material and were generally very large. This group includes the largest dinosaur ever discovered.[3]

Ornithischians (from Greek meaning "Bird hip") including four major groups:

Ankylosaurs - Heavily armored (extensive osteoderms), quadrupedal herbivores. Many species also had an associated bony club on the tail and/or shoulder spikes. They had exceptionally wide hips and large guts to digest plant matter.

Ceratopsians - Quadrupedal herbivores and omnivores that have distinctive head ornamentation. This often includes bony horns and neck crests. The neck crests may have been for defensive and/or display reasons. In some animals, the crests are simply a frame with large gaps that would have been filled with soft tissue. These would have provided little to no defense, but could have been filled with blood to give a vivid display. Another group that is closely related are the Pachycephalosaurs.

Ornithopods - Bipedal herbivores that are often known as the 'duck billed dinosaurs'. Many of them did indeed have duck-like bills along with elaborate head crests. It is likely that the head crests were used for species recognition and sexual display.

Stegosaurians - Quadrupedal herbivores with relatively small heads and armor plating. They are most well known for the bony plates (osteoderms) that often run along their backs and the presence of tail spikes (thagomizers).[3]

All dinosaurs are known to be terrestrial, with flight developing in theropods around the Middle Jurassic. There are no known marine dinosaurs, although trace fossil evidence suggests some species could swim well. The ancient marine reptiles, ichthyosaurs and plesiosaurs are, contrary to popular belief, not dinosaurs, and are in fact more closely related to modern lizards than to dinosaurs.

Exceptional preservation is required to preserve anything other than bone and teeth. This is exceptionally rare, but, despite this, a large number of theropod dinosaurs have been discovered with extensive downy feathers covering their whole bodies. They also had have been shown to have long display feathers on the forelimbs, tail ends, backs of their heads, and the back of the hips (depending on the species). It is, however, becoming more apparent that possibly all theropod dinosaurs had feathers. Some ceratopsians have also been discovered with 'quill' like structures along their hides. It is now being considered that quill-like structures evolved in early archosaurs and that the 'fuzz' on pterosaurs is related to both the ceratopsian quills and the theropod feathers. Preserved skin samples of some ornithopods and sauropods suggest that they at least partially lost these features and had a tough scaly hide.

The color of dinosaurs has long been a heated debate. Until very recently, it was impossible to determine the actual colors of a dinosaur. However, a new technique has been developed to accurately determine the color of feathered dinosaurs. This has so far only been used to completely establish the colors of the dinosaur Anchiornis huxleyi[4]. Since this technique can only be used on samples with exceptional preservation, there is still a wide scope for coloration among many groups of dinosaurs. Research is currently being done to color more species.

Although the dinosaur lineage still exists today in birds, dinosaurs underwent a massive extinction event approximately 65.5 million years ago. Their diversity was greatly reduced, with the loss of all ornithischians, all sauropods, and most of the theropods. The extinction occurred at the end of the Late Cretaceous (also the end of the Mesozoic). The extinction event is commonly known as the KT event (K representing Cretaceous and T representing Tertiary, which has since been renamed as the Paleogene) and it greatly affected many other groups too. Pterosaurs, mosasaurs, pliosaurs, plesiosaurs, belemnites, ammonites, and many others were all wiped out and plantic forams, calcareous nanofossils, land plants, and rudist bivalves were all severely affected. The extinction even had little to no visible impact on the insect populations[5].

There is still heated debate about the actual cause of the extinction event(s). The paleontological community is roughly equally divided among it. Although there is a prominent iridium layer present at the KT boundary (strongly suggesting a bolide impact), the associated tsunami deposits that should be associated with it don't seem to be present at sites across the world where they should be and there is still no impact crater recorded of the right size with the right age[6]. Many of the groups in question here were already in decline and there is also an associated volcanic event that occurred at the same time. This volcanic event is known as the Deccan Traps and undoubtedly would have had a significant impact on the planets climate and animals (as was shown with the Siberian Traps and the Permo-Triassic extinction). Research into the Deccan Traps is still ongoing. The currently accepted 'middle ground' is that it was probably a combination of events that lead to the final decline and extinction of these taxa.

There are many dinosaur characters present within the furry fandom as a popular scalie choice. The majority of these tend to be theropod dinosaur characters and are almost always based on the Jurassic Park misrepresentation of a Velociraptor with some feathers and quills stuck on. They also tend to be described as cold-blooded, due to a general misconception. Characters based on other species of dinosaurs are rare and complete fursonas based on them are even rarer.

In an attempt to expand public ideas of dinosaur character creation, Palaeofox developed the character 'Pecky'. Pecky is a Troodon formosus and so is somewhat similar morphological to a Velociraptor, but is more slender with a narrower snout and was probably an omnivore. His aim in developing this character was to allow furries to see that there are many different species of dinosaur they could base a character on, even if they specifically like the 'theropod look'.

Jurassic Park, is a book about an island where actual dinosaurs are created. As expected, things go a bit wrong and the dinosaurs escape out of their pens. They then wreak havoc on the various people who are in the park at the time. A total of three movies were made from the franchise.

The Dinotopia books feature humans living alongside dinosaurs in harmony on an isolated island, surrounded by a large storm over a reef that prevents contact with the outside world. The majority of the dinosaurs within the story are sentient and able to talk. This is due to magical glowing stones that keep order in their world. Dinotopia was also made into a TV miniseries.

Dinosaurs was an American TV sitcom, based around a family of anthropomorphic dinosaurs approximately 60 million years BC. The series concept was designed by Jim Henson a few years before his death, and it ran for 4 seasons between 1991 and 1994. Strangely, each member of the family seemed to be from a different species of dinosaur, and the few humans who appeared were portrayed as cavemen.

The Land Before Time (1988) is an animated film, featuring a cast of entirely anthropomorphic dinosaurs. It is the story of a group of hatchling herbivorous dinosaurs that are isolated from their parents in a dangerous and dying world. They set out on an adventure to find 'The Great Valley', where they will be reunited with their parents. The success of this movie spawned an astounding 12 more movies in which they have various adventures within The Great Valley itself.

Dinosaur (2000) is a CGI animated Disney film. A stolen dinosaur egg hatches into an iguanodon named Aladar, who is raised by lemurs on a lush island devoid of other dinosaurs. When a meteorite destroys their island home, the lemur family and Aladar become part of a dinosaur troop roaming the mainland deserts looking for the lush nesting grounds. All the animals are portrayed as anthropomorphic, given human voices and characteristics.